Hygrometer



Feb. 19 1924.

A. HERMANN ET AL HYGROMETER Filed March 17 INVENTORS CARL A. MENZEL A TTORNEYS.

Patented Feb.,19,

- UNITED STATES PATENT OFFICE.

ALBERT HERMANN, or M DISON, wIsCoNsIN, AND CARL A. MENZEL, or CHICAGO, ILLINOIS, DEDICATED, BY MESNE ASSIGNMENTS, 'ro THE PEOPLE or THE UNITED STATES OF AMEBIGA,

nronomn'rnn.

Application filed larch 17, 1923. Serial No. 625,870.

(FILED UNDER, THE ACT-F MARCH 3, 1883, 22 STAT. L, 625.)

Avenue, Chicago, Illinois), have invented a,

new and useful Hygrometer.

This application is made under the act of March 3, 1883, chapter 143 (22 Stat, 625), and the invention herein described and claimed ma be used byv the Government of the United States, its otiicers and employees,

and by any person in the United States without pa ment to us of any royalty thereon. e hereby dedicate the same to the free use of the Government and the people of the United States.

This invention consists-of a new and use ful apparatus for producing and maintaining t e psychometric wet bulb temperature in and surrounding the temperature-sensitive elementsof instruments which indicate, 80 record, control or regulate temperature through the action of temperature-sensitive elements placed directly in the atmosphere whose temperature is to be measured or humidity controlled. It is well known that .a 85 wet surface ex osed to a curren'tof air will be cooled to a efinite temperature, known as the wet bulb tem erature. The amount of cooling (the wet ulb depression) depends upon the amount of humidity in the atmos- 4 phere and the humidit can be determined, through theuse of tab es or formulae. when the actual or dry bulb temperature and the wet bulb temperature are known. Wet bulb thermometers and thermostats are common-1y 48 used for the measurement and control of humidity, there being several means employed for keeping the bulbs-or temperature-sensitive elements wet; The most common of these is the wet wick. This wick is usually a piece of cloth or a knitted'tube of fibrous hygroscopic material surrounding the temperature-sensitive element and dipping into a water reservoir mounted directly under the temperature-sensitive element. The wick is kept wet by capillary act-ion so long as the water reservoir 15 kept supphed and the wick remains reasonably clean. It is found diflicult, in practice, to meet both of these requirements and practically impossible, in the case of extension tuberecording thermometers and thermostats, to devise a satisfactory portable reservoir and wick arrangement.

In the present invention, a porous receptacle replaces the customary wick and special arrangements are provided for the water supply. This receptacle may be of fibrous or non-fibrous material, with or without hygroscopic properties. It is well known that water contained in porous earthen/ware vessels set in a breeze will become cooled to a temperature below that of the surrounding atmosphere. This effect is produced by the evaporation of small quantities of water which see through the porous walls of the vessels. he amount of cooling depends upon the strength of the breeze, the porosity of the vessel and the humidity of the surrounding atmosphere.

Experiments have shown that, using porous'receptacles of alundum and an office fan to produce air-movement, it is possible to reduce the temperature of the porous receptacle and the water in it accurately tov the wet bulb temperature of the surrounding atmosphere. A considerable excess of water dripping from the bottom of the porous receptacle does not interfere with the accuracy of the method. In the practical application of this invention the temperature-sensitive element of the thermometer or thermostat of whatever type is inserted in theorous receptacle which is kept filled with water to a specified level in any convenient manner'or is supplied, in certain types, with water under pressure.

In the accompanylng drawings, illustrating our invention and its a plication, Figure 1 shows the adaptation o the invention to an extension tube thermometer or thermostat with pressure water supply; Figure 2 shows the adaptation of the invention to-an extension tube thermometer or thermostat with an open-top porous receptacle and vacuum water su ply; and Figure 3 shows the adaptation o the invention to a glass indicating thermometer. Similar letters of the instrument.

refer to similar parts throughout the three figures.

In Figure 1, A is the porous receptacle, which may be of earthenware, alundum,"carborundum, emery, or other suitable material; B is a packing gland making a water-tight joint between the porous receptacle'A and the outside tube C; C is a flexible watertight conduit through which water is supplied to the porous receptacle A;'this conduit acts as a protecting armor or sheath for the capillary extension tube K; both conduit and tube may be of anyv convenient length, usually from 10 to 100 feet. I) is a pipe connecting the conduit C with the water main F; E is a valve inthe pipe D,

adapted to regulate and control the supply of water to the conduit C; F is the water main or supply line which supplies water at suitable pressure to the pipe D; G is a fitting permitting the capillary extension tube K to pass into the instrument ease H and preventing the passage of water from the pipe D or the conduit C into the instrument case A; H is the case of the instrument, which may be either thermostat or thermometer of suitable design; K is the capillary tube connecting the instrument case H with the temperature-sensitive element I; I'is the temperature-sensitive bulb the variations in whose temperature actuate the mechanism of the instrument. This temperature-sensitive element may be filled with gas, Vapor, mercury, or other suitable substance, or may be of the differential ex ansion type or other well-known type. I is the capillary extension tube connecting the temperaturesensitive element I'with with the case H The mechanism-within the case H may be of any type used with wise be an instrument which both indicates or records temperature and regulates humidity.

In Figure 2, A, H, I, and K are similar to similarly lettered parts in Figure 1. L is i a water bottle and M a tube fitted into the water bottle with its lower end extending into the porous receptacle A. This arrangement automatically keeps the water vel at the lower end of tube M so long as any water remains in the water bottle L.

In'Figure 3, A,L and M are similar to similarly lettered parts in Figure 2. N is a glass indicating thermometer of any one of the usual types. 1

Having described and illustrated our invention and its application, we claim;

1. A wet-bulb thermometer consisting of a receptacle having porous rigid walls, a thermometer whose temperature-sensitive element is mounted within and spaced from the walls of said receptacle and means asso-' ciated with said receptacle and adapted at all times to maintain a body of liquid between said element and said porous receptac e.

2. A wet-bulb extension tube thermometer consisting of a receptacle having porous rigid walls, a conduit adapted to supply liquid to said receptacle, and an extension tube thermometer whose temperature-sensitive element ismounted in said porous receptacle and whose extension tube is contained within said conduit.

' CARL A. MENZEL.

ALBERT HERMANN. 

